Lindsay Lohan -- I'm No Hit-and-Runner

Lindsay Lohan is calling BS on a hookah lounge manager, who claims the actress injured his knee when she allegedly grazed him with her Porsche last night -- insisting, "This is all a complete lie."

Lindsay took to her Twitter account moments ago to blast the allegation -- writing, "Scrape? This is all a complete lie. I've been at community service. Last night, I attempted to wish a friend happy birthday, which I didn't even get to do because I was freaked out by all of the paparazzi."

Lindsay insists, "These false accusations are absurd."

A rep for Lindsay adds, "At no point was there ever any indication that her car hit anyone or anything. We are confident this matter will be cleared up in the next few days."

TMZ broke the story ... multiple eyewitnesses claim Lindsay struck the hookah lounge manager on her way out of The Sayers Club in Hollywood just after midnight.

Witnesses claim the manager was NOT injured after the bump -- but the man has since gone to the emergency room. We're told he plans to press charges.

1:00 PM PT: Lindsay just left the L.A. County morgue in the same black Porsche she was driving last night -- except this time, she wasn't taking any chances ... getting into the passenger seat.